TORUŃ, POLAND—Underwater archaeologist Krzysztof Radka of Nicolaus Copernicus University and his team were surveying the remains of one of two medieval bridges leading to the Ostrów Lednicki, an island in Lake Lednica, when they discovered a large, wicker fish trap. The oblong trap, found in the remains of the bridge to the east of the island, contained the remains of more than 4,000 fish. “Exploration required extreme caution because the wicker basket could disintegrate with every movement of water. [The] extraction operation was complicated because of the size, state of preservation, and delicacy of the object, but it seems that it was successful,” Radka told Science & Scholarship in Poland. “It is the only relic of the ninth-tenth century found during underwater research in Poland,” he explained. The bridges were destroyed in 1038 when Czech prince Bretislav invaded and captured the city of Poznań, on the western side of Lake Lednica, and sacked the city of Gniezno, on the eastern side. To read about the medieval fish trade in London, go to "Off With Their Heads."